Blood pressure is the force exerted by circulating blood on the walls of your arteries.

A useful analogy is the water pressure inside a garden hose.

It is measured in millimetres of mercury (mmHg) and is expressed as two numbers:

• Systolic (top number)
  This is the pressure in your arteries when your heart beats (contracts) and pumps blood into the body.
• Diastolic (bottom number)
  This is the pressure in your arteries when your heart relaxes between beats and refills with blood.

You could think of the heart as a pump.

Why is knowing your Blood Pressure (BP) important?

Most people understand that high blood pressure is not good for them.

It is a major contributing factor to:

• strokes
• heart attacks
• heart failure
• kidney failure
• dementia
• loss of vision
• peripheral artery disease
• sexual dysfunction

What numbers are considered to be High Blood Pressure?

With that in mind, you might expect a clear definition of what constitutes “high blood pressure”.

In practice, it depends on which guidelines are used.

European guidelines

According to the European Society of Cardiology and European Society of Hypertension:

• Optimal: less than 120 systolic and less than 80 diastolic
• Normal: 120–129 systolic and/or 80–84 diastolic
• High-normal: 130–139 systolic and/or 85–89 diastolic
• Hypertension: 140 or higher systolic or 90 or higher diastolic

United States guidelines

According to the American Heart Association and American College of Cardiology:

• Hypertension: 130/80 mmHg or higher
• Stage 1 hypertension: 130–139 systolic or 80–89 diastolic
• Stage 2 hypertension: 140 or higher systolic or 90 or higher diastolic

The practical difference between Stage 1 and Stage 2 relates to how urgently treatment, including medication, may be considered.

• Hypertensive crisis (medical emergency):
  higher than 180 systolic and/or higher than 120 diastolic

How do I determine which BP level is right for me?

There is no single number that applies to everyone.

The difference between US and European definitions does not reflect disagreement about how blood pressure affects the body. Rather, it reflects different approaches to when to intervene.

The US guidelines take a more aggressive stance and tend to act earlier.

To understand why, it helps to look at a major clinical study.

The SPRINT trial

(Systolic Blood Pressure Intervention Trial)

• Enrollment began: 2010
• Follow-up: 2010–2015
• Stopped early: August 2015 due to clear benefit
• Participants: ~9,300
• Age: 50 and above
• All had elevated cardiovascular risk, but no diabetes

Participants were randomly assigned to:

• Standard treatment: target systolic BP below 140 mmHg
• Intensive treatment: target systolic BP below 120 mmHg

Importantly, blood pressure in SPRINT was measured using automated, unattended devices, which tend to produce slightly lower readings than typical clinic measurements.

Results

The trial was stopped early after approximately 3.3 years because of clear benefit in the intensive group.

Compared to standard treatment, the intensive group had:

• ~25% lower risk of major cardiovascular events
  (heart attack, heart failure, stroke, cardiovascular death)
• ~27% lower all-cause mortality

Trade-offs

There were also some downsides in the intensive group:

• Low blood pressure symptoms (such as dizziness or fainting)
• Electrolyte abnormalities
• Acute kidney injury

The increase in kidney-related events was modest (about 3% higher). Many of these cases were reversible, though still clinically significant and requiring monitoring.

What can we conclude?

In higher-risk individuals, lower systolic blood pressure was associated with:

• Fewer heart attacks and heart failure events
• Lower cardiovascular mortality
• Lower overall mortality

However, this is not a one-size-fits-all situation.

For many higher-risk individuals, lower blood pressure can provide additional benefit, if tolerated safely

What about lower-risk individuals?

For those who are:

• Young or middle-aged
• Without diabetes
• Without established cardiovascular disease
• With normal or near-normal kidney function
• With a favorable lipid profile (including ApoB)

A more moderate approach is appropriate.

A systolic blood pressure in the range of approximately 110–125 mmHg is generally reasonable if achieved without symptoms such as dizziness or reduced kidney function.

It is important to understand that cardiovascular risk does not suddenly begin at 140 mmHg. It increases gradually as systolic pressure rises above about 120 mmHg.

Final note

Always consult a qualified healthcare professional before making any changes to medications or lifestyle.

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